Human mycoplasmas have been isolated from joints of patients with arthritis. Arthrogenic mechanisms suggested in animal mycoplasmas can~t be generalized. Chimpanzees have been suggested as a model of studying the human mycoplasmosis. Experimental interarticular (knee) inoculation in these non-human primates with Mycoplasma hominis 1620 and 1628, Mycoplasma pneumoniae 1428 and Ureaplasma urealyticum 2010 B (all isolated from human joints) resulted in a similar sign of joint disease as found in humans. Sera of these chimpanzees was obtained before and after infection along 8 to 15 weeks. Samples of synovial fluids were included in this study. The purpose of this project is to detect the immunodominant proteins of these strains of mycoplasmas. These data will be helpful for vaccine development and the mycoplasma/host relationship understanding.